Update cheatsheet.fr.md

12.temporary_ins/08.grad-div-rot/70.combinaisons-of-operators/20.overview/cheatsheet.fr.md

@@ -69,13 +69,15 @@ PRINCIPALES COMBINAISONS
       <summary>Expressions en coordonnées cylindriques et sphériques</summary>
       * coordonnées cylindriques $`(\rho\,,\,\varphi\,,\,z)`$ :   
         <br>
-       $`\Delta\,\phi=\dfrac{1}{\rho}\dfrac{\partial}{\partial \rho}\left(\rho\,\dfrac{\partial \phi}{\partial \rho}\right)
-        +\dfrac{1}{\rho^2}\dfrac{\partial^2 \phi}{\partial \varphi^2}+\dfrac{\partial^2 \phi}{\partial z^2}`$
+       $`\Delta\,\phi=\dfrac{1}{\rho}\cdot\dfrac{\partial}{\partial \rho}\left(\rho\,\dfrac{\partial \phi}{\partial \rho}\right)`$
+        $`+\dfrac{1}{\rho^2}\cdot\dfrac{\partial^2 \phi}{\partial \varphi^2}`$
+        $`+\dfrac{\partial^2 \phi}{\partial z^2}`$   
+       <br>
       * coordonnées sphérique $`(r\,,\,\theta\,,\,\varphi)`$ :   
         <br>
-       $`\Delta\,\phi=\dfrac{1}{r}\dfrac{\partial^2}{\partial r^2}(r\phi)+
-         \dfrac{1}{r^2\,\sin\theta}\dfrac{\partial}{\partial \theta}\left(\sin\theta\dfrac{\partial \phi}{\partial \theta}\right)+
-         \dfrac{1}{r^2\,\sin^2\theta}\dfrac{\partial^2 \phi}{\partial \varphi^2}`$
+       $`\Delta\,\phi=\dfrac{1}{r}\cdot\dfrac{\partial^2}{\partial r^2}(r\phi)`$
+       $`+\dfrac{1}{r^2\,\sin\theta}\cdot\dfrac{\partial}{\partial \theta}\left(\sin\theta\dfrac{\partial \phi}{\partial \theta}\right)`$
+       $`+\dfrac{1}{r^2\,\sin^2\theta}\cdot\dfrac{\partial^2 \phi}{\partial \varphi^2}`$
 
 
    ---